The present invention is related to LVDS circuits. More particularly, the present invention is related to an LVDS driver circuit that provides various biasing currents by sensing the output current in a load resistor.
Low Voltage Differential Signaling (hereinafter referred to as LVDS) is a technology used in data transmission systems. A low voltage differential signal produced by a line driver that typically has a peak-to-peak amplitude that is in the range from 250 mV to 450 mV. The low voltage swing helps to minimize power dissipation, while maintaining high transmission speeds. Typical transmission speeds exceed 100 Mbps (Mega-bits per second).
LVDS technology is particularly useful for high-speed data transfer applications such as video data processing. LVDS technology may be found in professional video processing equipment, and consumer electronics such as camcorders and laptop computers, to name a few. Consumer electronics typically have tighter cost constraints compared to professional video processing equipment. Moreover, many consumer electronics devices have small form factor requirements based on various ergonomic considerations.
The density of circuits (board level, hybrid, and/or integrated circuit) is increasing to satisfy the need for smaller form factors. The increased density of the circuits may result in special requirements for packaging and heat dissipation. For integrated circuits, the physical size of the integrated circuit (i.e., the xe2x80x9cdie areaxe2x80x9d) is often a large contributing factor in the cost.
Bonding pads are required on integrated circuits (ICs) to make each connection to external pins in the packaging material. Often times, the bonding pads on the integrated circuit (i.e., the xe2x80x9cdiexe2x80x9d) take up a substantial amount of area such that the xe2x80x9cdie-areaxe2x80x9d is said to be xe2x80x9cpad limitedxe2x80x9d. Modem technologies such as micro-SMD, and flip-chip suffer from pad limited die areas such that the number of available pins are a determining factor for the total area of the die, and hence a dominant factor in cost. The packaging costs and form factor requirements are often constrained by the pin interface requirements for the IC.
In some instances, it is impractical (either in terms of cost or feasibility) to include certain components in the integrated circuit. For example, conventional integrated circuit technology makes it impracticable to include filter capacitors in the microfarad range xe2x80x9con-chipxe2x80x9d. In other instances, it is desirable to keep certain components xe2x80x9coff-chipxe2x80x9d so that the integrated circuit can be easily configured by user selection of the component value.